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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17859, 17860, 17861
Message-Id: <20260701070804.D961928808EB@server.astronomerstelegram.org>
Date: Wed,  1 Jul 2026 03:08:04 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17859							     ATEL #17859

Title:	EP260628c: Einstein Probe detection of an X-ray transient
Author:	H. N. Yang, X. Mao, C. C. Jin (NAO, CAS), C. Y. Dai (NJU)
		on behalf of the Einstein Probe (EP) team
Queries:	ep_ta@bao.ac.cn
Posted:	30 Jun 2026; 09:07 UT
Subjects:X-ray, Transient

We report on the detection of an X-ray transient by the Wide-field X-ray
Telescope (WXT) on board the Einstein Probe (EP) mission through ground
data analysis, designated EP260628c. The transient was firstly detected
in the WXT observation starting at 2026-06-28 16:22:49 (UTC). The WXT position
of the source is R.A. = 339.500 deg, Dec = 53.226 deg (J2000) with an uncertainty
of 2.7 arcmin in radius (90% C.L. statistical and systematic), located
at low Galactic latitude (l = 103.648, b = -4.576). The 0.5–4 keV spectrum
obtained in this observation can be fitted with an absorbed power-law model
with the hydrogen column density of 7.6 (+1.5/-7.6) x 10^21 cm^-2 and photon
index of 1.7 (+2.2/-1.6). The absorption-corrected 0.5-4 keV flux is 1.3
(+7.6/-0.6) x 10^-10 erg cm^-2 s^-1.

The Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission
performed a follow-up observation on 2026-06-29 13:02:00 (UTC), with a
net exposure of 2.5 ks. A bright uncatalogued X-ray source was detected
within the WXT error circle at R.A. = 339.4980, and Dec. = 53.2394 (J2000),
with an uncertainty radius of 10 arcseconds (90% confidence level, including
both statistical and systematic uncertainties).

The FXT spectrum can be fitted with an absorbed power-law model. The best-fitting
parameters are a hydrogen column density of 6.28 (+/-0.02) x 10^21 cm-2
and a photon index of 1.99 (+/-0.04). The absorption-corrected 0.5-10.0
keV flux is 1.61 (+/-0.03) x 10^-10 erg/s/cm^2. Using the barycenter-corrected
light curve of this source, we can identify a significant periodic signal
of approximately 3 seconds.

Further follow-up observations are encouraged to identify the nature of
this source.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor
the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook
of X-ray and Gamma-ray Astrophysics).

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Password Certification: Yuan Liu (liuyuan@bao.ac.cn)
https://www.astronomerstelegram.org/?read=17859
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ATEL #17860							     ATEL #17860

Title:	A flare of the H2O maser W31(1)
Author:	Ashimbaeva, Nuriya, Lekht, Evgeny (Moscow State University,
		Sternberg Astronomical Institute), Shoutenkov, Vladimir (Pushchino
		Radio Astronomy Observatory, Astro Space Center, Lebedev Physical
		Institute, Russian Academy of Sciences)
Queries:	nta2@yandex.ru
Posted:	30 Jun 2026; 23:43 UT
Subjects:Radio, Request for Observations, Young Stellar Object

We report a flare from the source of maser radio emission at 22.235 GHz
in W31(1) (also known as G010.5+0.023 and G01.47+0.27). From the catalogue
of F. Han et al. (1995, Purple Mountain Observatory, 14, 185), the coordinates
of the source are RA J2000 = 18 08 38.418, DEC J200 = -19 51 51.69. The
source is associated with an ultracompact H II region at a distance of
about 5.8 kpc (P. Hofner & E. Churchwell, 1986, ApJ, 375, L25).  
Observations were carried out using the 22-metre radio telescope at Pushchino,
Russia, and monitoring of this object began in mid-2016. 
The flare spectrum contains a strong peak at VLSR = 68.6 km/s. The history
of its flux density variations in 2026 was: Feb 18 - 100 Jy; Mar 18 - 63
Jy; Apr 15 - 244 Jy; May 27 - 287 Jy; Jun 23 - 5117 Jy;  Jun 24 - 5678
Jy; Jun 25 - 3550 Jy (there were bad weather conditions on the last day,
it rained and there is a possibility that this affected the decrease in
flux). In this case, the intensity in the line at VLSR = 58.8 km/s remained
practically unchanged and was about 250 Jy.

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Password Certification: Nuriya Ashimbaeva (nta2@yandex.ru)
https://www.astronomerstelegram.org/?read=17860
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ATEL #17861							     ATEL #17861

Title:	Four solar flares from four different regions and X1 flare
		culminates the solar activity on 30 June 2026 
Author:	Costantino Sigismondi
Queries:	sigismondi@icra.it
Posted:	30 Jun 2026; 23:54 UT
Subjects:Radio, Optical, Ultra-Violet, The Sun

Four solar flares from four different regions and X1 flare culminates the
solar activity on 30 June 2026

The solar activity in the last 48 hours has been characterized by several
flares from different active regions. 
A similar situation occurred on 3 November 2025 when the superflaring region
AR 4274 started with an M5 flare (ATel #17494). 
From 12:30 to 13:30 UT of 30 June 2026 four consecutive flares, reliably
sympathetic, involved the active regions no. 4478, 4480, 4475 (M5.8, long
duration event) and 4479 ( https://youtube.com/shorts/0gf9btA-KOg from
Kanzelhohe Observatory). 
AR 4478 and 4479 are classified as Beta-Gamma-Delta region, the former
active since 23 June, the latter has been more active since the end of
28 June, but its predominance was in competition with AR 4475 (near the
same solar longitude of ATel #17851). 
The region AR 4478 is Southern and it has reached, on 30 June, the significant
dimension of 1300 millionth of solar hemisphere, becoming one of the largest
of the present solar cycle, but since 23 June to 30 June its 22 flares
are all of C class, topping with C9.1 at 19:58 of 30 June. This triggered
the X1.1 flare at 21:00 UT on AR 4479 at the Northern hemisphere. The two
regions AR 4478 and 4479 appear to be sympathetic. 
In the sequence of flares of AR 4479 the most relevant are: 28 June C8.7
at 21:59 UT, 29 June C8.1 (long duration event) at 8:28 UT, M1.4 at 21:40
and M1.3 (1F optical importance) at 13:36 UT of 30 June, during the M5.8
of AR 4475 and X1.1 at 21:00 UT. 
If the region AR 4479 predominates for 3 days (ATel #17852) the flare X1.1
can be its strongest one, but the sympatheticity with AR 4478 may activate
new strong flares on it.

X-rays from GOES and LMSAL data of 30 June 2026 (PDF): https://drive.google.com/file/d/1QIcyaT7kGDFaiZNE-I_5zEKGzbnW9r5q/view?usp=sharing
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Password Certification: Costantino Sigismondi (sigismondi@icra.it)
https://www.astronomerstelegram.org/?read=17861
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